Andrea

TROPICAL STORM ANDREA JUNE 5-7, 2013    

During the early evening of June 5, 2013, Tropical Storm Andrea formed in the east-central Gulf of Mexico becoming the first named storm of the 2013 tropical season, and over the next 48 hours, Andrea would pummel portions of south Florida with heavy rainfall and major flooding.  Andrea even spawned three tornadoes including an EF-1 tornado that tore through portions of northeast Palm Beach county (Image 2).  Through its lifespan, Andrea moved in a steady north to northeast fashion and eventually made landfall across the Big Bend portion of northern Florida on the afternoon of June 6th.  Shortly before making landfall, Andrea's winds peaked at 65 mph and actually attained its lowest pressure of 992 millibars just after making landfall.  On June 7th, Andrea then weakened and became extratropical as it continued to push northeast across northern Florida, Georgia, and the Carolinas.

Although Andrea never made landfall in south Florida, it had far reaching impacts that mainly affected the east coastal areas.  During the early morning hours of June 6th, convective rain bands well to the southeast of the storm center streamed across the south Florida area spawning three tornadoes.  The first occurred just after 3 AM and affected the town of Belle Glade in Palm Beach county.  Only minor damage to trees and power lines was sustained from this tornado and was rated as an EF-0.  Just a few hours later, another tornado ripped through The Acerage community in north central Palm Beach county.  This tornado damaged several homes and snapped trees and power lines as it tracked across a residential area just west of 130th Avenue between 69th Street and 87th Street (Image 5).  Most of the damage sustained by homes was in the form of roof damage.  The garage door of one home was damaged causing the door to blow in, leading to the roof being completely punctured above the garage.  A few vehicles were also moved from their original locations and a 30-foot boat was flipped on its side.  There was one serious injury sustained by this tornado that required hospitalization.  An 85 year-old woman was struck by flying debris from a large oak tree that broke through her bedroom window.  According to the National Weather Service damage survey, this tornado was rated as an EF-1 with maximum sustained winds of 100 mph.  A third tornado touched down across inland Broward county just east of U.S. Highway 27 about 6 miles north of Alligator Alley and tracked north, likely crossing over into southern Palm Beach county.  This tornado was rated as an EF-0.

The same convective rain bands that spawned these tornadoes also produced major flooding as they trained across extreme northeast portions of Miami-Dade county and southeast Broward county during the evening of June 7th.  Bands of very heavy rainfall trained over the same area for hours producing over a foot of rain in some locales.  This excessive rainfall caused widespread flash flooding with roads becoming impassable along with numerous disabled vehicles (Image 4).  Water entered homes as well, prompting a couple of dozen families to be relocated.  The table below indicates total 24 hour rainfall amounts in inches for various locations.

NWS Miami Performance:

1.  Tornadoes 

A total of 9 Tornado Warnings were issued across South Florida in association with Tropical Storm Andrea, all during the overnight and early morning hours of June 6th. Three tornadoes were confirmed, one EF-1 tornado and two EF-0 tornadoes.  All tornado events were warned for with an average lead time of 7 1/2 minutes. Below is a summary of each tornado's issuance time, time of occurrence and warning lead time. 

Computer models suggested a tornado potential about a week in advance of Andrea even developing.  Given the potential seen by forecasters in the computer models, the threat of potential severe weather was first mentioned in the Hazardous Weather Outlook (HWO) on the morning of June 1st.  Subsequent issuances of the HWO included the severe weather potential, with even the threat of tornadoes mentioned from the June 2nd then leading up to the torando event. 

2.  Flash Flooding

Flash flooding took place during the late afternoon and evening of June 7th across northeastern Miami-Dade County and southeastern Broward County associated with a tropical moisture plume south of Andrea. The highest rain total was 13.96 inches at North Miami Beach as shown in the table above.

A Flash Flood Warning was issued at 3:38 PM EDT on June 7th.  After about 4:15 PM, flood reports began to come in and at 4:53 PM, the Aventura Police Department reported impassable roads.  At 5:17 PM, they reported some 50 vehicles disabled due to the flooding.  At 5:30 PM, hundreds of people were reported stranded in Golden Beach due to the flood waters inundating numerous roads in the area.

Computer models suggested the potential for flooding before Andrea developed, given deep tropical moisture which was poised to move into South FL.  Timing of the flood threat was a challenge as localized heavy rains were a possibility for days leading up to the actual flash flooding which occurred. The Hazardous Weather Outlook reflected the locally heavy rainfall/flooding potential beginning on June 1st.